I am updating my website to be responsive. And able to fill also large computer screens. Previously - some years ago - it was needed to make the photos as small as possible, mostly because You did not want people to abandon Your site, if it took too long to open due to too large photos loading. I made most of the photos size 10-20 kb...
What about today? What is an optimal size, considering the pc power people have now, and also considering the full screen and responsive option as mentioned above?